Windpuffs in Horses

These fluid-filling swellings often are just blemishes, but attention should be given if they are new or associated with lameness.

Windpuffs are soft, fluid-filled swellings toward the back of the fetlock joint, resulting from inflamed deep digital flexor tendon sheaths. Most commonly, these puffy enlargements are symptomless blemishes--old and cold, the result of years of hard work. In some instances, however, the horse might be lame from recent injury to the tendon sheath, with marked heat and pain in the area, when you flex the joint or palpate the swelling.

"The swellings occur where the digital flexor tendon sheath covers the two tendons that go around the back of the fetlock," says Lynch. "This sheath has a synovial lining, just like a joint."

Tendons, especially where they glide over a hard surface such as bone, are always lubricated to prevent friction that might interfere with smooth movement. Wherever a tendon runs across a joint, such as the fetlock joint, the tendon is encased in a hoselike sheath that contains a small amount of lubricating fluid. Swelling in this area of the fetlock generally means the sheath or the structures within it have been stretched or injured and has created extra fluid. This causes the sheath to bulge like a balloon. In chronic cases the sheath lining will remain thickened, and fluid levels will vary with the horse's exercise levels.

"The whole area may be swollen on both sides, or perhaps just one side," says Lynch. "Most windpuffs are chronic, and most horses with windpuffs are not lame, though it's a sign of overextension or tearing/pulling of the sheath, or maybe the tendons themselves.

"A chronic windpuff can turn into an acute one if it gets re-injured or stretched," adds Lynch. "There are often some adhesions between the tendons and sheath, so these may be vulnerable to tearing and a new injury."

"The key to whether windpuffs are a problem is whether they are symmetrical," says Gary Baxter, VMD, MS, Dipl. ACVS, professor of surgery in Colorado State University's College of Veterinary Medicine and Biomedical Sciences. Many horses have windpuffs on all four legs, or both hind legs. "If they are symmetrical, I am usually not concerned. But if one is much larger (in one leg compared to the others), this usually indicates a problem, such as acute injury in that leg," he says. If a horse has chronic windpuffs, it is important for owners to notice if one becomes obviously larger. Baxter advises having a veterinarian check the leg if you notice more swelling.

Tenoscopy

Putting an arthroscope into the tendon sheath (tenoscopy) often reveals more than an ultrasound does, and your veterinarian has the added advantage of being able to treat a problem at the same time when he or she uses this procedure. "Horses with chronic problems within the tendon sheath may have extra buildup of synovial tissue," says Gary Baxter, VMD, MS, professor of surgery at Colorado State University's College of Veterinary Medicine and Biomedical Sciences. "These soft tissue masses may cause pain with the movement of the tendon and should be removed. Whatever we find can be dealt with arthroscopically; we can often remove any soft tissue masses and cut the annular ligament at the same time, if needed.

"The other option is to make a small incision over the annular ligament to reach in and cut it, but you don't get a view of anything else," Baxter continues. "We generally recommend using an arthroscope and taking a look in there to view the tendon sheath and anything else that may be going on. Sometimes you can't see the tendon injuries unless you look inside with an arthroscope, because they are not always visible on ultrasound.

"Some cases can be problematic, with chronic swelling and tendonitis, and some of these horses are quite lame," states Baxter. "If there's chronic inflammation we generally utilize tenoscopy. Whether or not you'd do an MRI before this surgery would depend on the case. The owner may not be able to afford both. If you have to do one or the other, I'd rather do tenoscopy because then I could fix the problem at the same time I am looking inside the sheath with the arthroscope."

--Heather Smith Thomas

Occasionally the fetlock joint capsule (rather than the tendon sheath) is swollen. This enlargement is situated between the cannon bone and suspensory ligament, just above the sesamoid bones. Windpuffs are more to the rear. Both types of swellings can appear together, caused by intense training, exercise on hard surfaces, strain, and stress (sometimes aggravated by poor leg conformation, such as upright pasterns or club foot, that puts even more strain and concussion on the support structures), but in most cases there is no lameness.

New, firm windpuffs on a lame horse, with heat and pain, are indicative of an injury that needs treatment. This might happen after a serious strain, as when the horse pulls the joint attachments while sprinting and turning, making fast stops and turns, etc. After healing, the stretched area continues to bulge, but it becomes soft and painless. Windpuffs usually appear, however, without the horse ever showing any evidence of lameness.

Gayle Trotter, DVM, MS, Dipl. ACVS, focuses his practice on equine lameness and orthopedic surgery in Weatherford, Texas. He says most horses with windpuffs show no soreness, even after a flex test. "But a small percentage show a little soreness for the first few steps when you jog them after flexion," says Trotter. "There are a few with more persistent lameness. Many of those have a problem in the annular ligament--a thin, flat sheet cupped around the back and bottom of the fetlock area."

If the annular ligament becomes thickened and inelastic it tends to pinch the tendons when the horse is working. "Some cases respond adequately to injections of hyaluronic acid (HA) in the tendon sheath," says Trotter, but some might need surgery if they don't improve after injections. In such cases, surgeons cut the thickened ligament so it doesn't inhibit the tendons.

Diagnosis

"Your veterinarian can determine if windpuffs should be looked at more closely with ultrasound or are something you don't need to worry about," says Trotter. "If the horse is lame, you need to find out why." If ligaments are torn or if tendon avulsion occurs, prognosis is not good. "Ultrasound and X rays can be used (to view the area). There can be some unusual bony problems in the sesamoids that contribute to swelling, but it's usually a soft tissue problem, and ultrasound is the best diagnostic tool."

Lynch adds, "In looking at windpuffs, we want to know the history. Has the swelling been there a long time, or is it new? If the horse is lame we need to look at all the structures--tendons, suspensory ligament, sheath, adhesions--to see if there is anything that might indicate a recent injury rather than something old and chronic."

Baxter says it's important to realize a horse with lots of fluid or more swelling in one leg than the other might have injury to the tendon within the sheath. "This needs to be properly diagnosed because this type of injury needs to be treated differently than a simple windpuff," he says.

The owner often can give the veterinarian a clue about whether there's been a change in the windpuff that might correlate with the lameness.

"An upper level jumper that's had windpuffs as long as you've owned him might suddenly come up lame and the windpuff on that leg might be a little bigger. It may have a little heat or pain when you palpate it or flex the ankle," says Lynch. You should report these changes to your veterinarian.

Trotter says often the first thing you'll notice is a performance change rather than actual lameness; the horse isn't giving his best effort. "If there's a change (in performance) and the puffiness appeared at the same time, the horse should be examined in case there's damage that needs medical attention," explains Trotter. "But if all you see is puffiness and the horse is working fine, this is just a work-related blemish."

Lynch often sees windpuffs in hunters, jumpers, dressage horses, and Western performance horses. "Sometimes you never know what causes them," he says. "If it's something new and the horse is lame, it's wise to do a complete lameness exam. (The veterinarian) can block the sheath (injecting lidocaine directly into it to see if this relieves the pain) and ultimately ultrasound the structures to help you make a better decision about treatment. Often, with old windpuffs in athletic horses, if the horse is now lame in one leg we might find adhesions or annular ligament desmitis. The ligament and surrounding tissue becomes thick and puts pressure on the tendon sheath."

Narrowing that impedes the gliding of the tendon (such as adhesions, synovial masses, or pressure caused by thickening of the annular ligament--as in humans with carpal tunnel syndrome) can result in lameness.

"Most horses that require annular ligament surgery have a characteristic appearance to the leg," says Baxter. "There is a notch, with fluid above and below the restriction. Ultrasound can help determine whether the annular ligament is normal thickness or not."

It's important to determine exactly where the swelling is--in the joint or tendon sheath (farther back)--since these are two separate compartments. "Windpuffs may also have a lopsided look," says Lynch. "Many horses have more swelling or thickness on the medial side (inside) of the leg in that sheath."

Prepurchase Exams

During a prepurchase exam, windpuffs are probably something that should be noted in light of what the horse does for a career. But as long as he is not lame and is able to do what he's supposed to do, these enlargements are usually disregarded.

"You need to palpate them very well to make sure there is no knot or mass in that enlargement, if you are buying the horse," says Tim Lynch, DVM, Dipl. ACVS, who focuses on equine lameness cases at Peterson & Smith Equine Hospital in Ocala, Fla. "Windpuffs usually don't scare the veterinarian or the new owner, especially if the horse is an older hunter or any horse that's had a strenuous career."

For most horses these are just blemishes. Whether or not you should ultrasound windpuffs for a prepurchase exam would depend on the situation and athletic use of the horse.

--Heather Smith Thomas

Baxter says that while ultrasound and tenoscopy (using an arthroscope to peer inside the tendon sheath; see sidebar on page 60) are the primary tools for diagnosis, MRI also can be used. "In a problematic case, this could help us figure it out, since we can document a lot more problems in the tendon sheath with an MRI," he says. Some owners won't want to go to this expense, but if it's a valuable horse with an important career, MRI can be an option.

Treatment

If there's excess fluid in the sheath due to acute injury or scar tissue, and it's causing discomfort, the horse might need treatment. With an acute injury the first step is resting the horse and using ice or bandaging, just as you'd do for a human with a sprained ankle or muscle injury "The most likely scenario is hyperextension of the fetlock joint, pulling the tendons, or a twist or sprain of structures around the tendon sheath," says Baxter. "Along with cold therapy and wrapping, you could use a topical anti-inflammatory medication such as Surpass (diclofenac sodium)." This will often resolve a simple strain/sprain.

If the problem does not respond to rest and wrapping or support boots, you can inject windpuffs with steroids and hyaluronic acid, similar to how you'd inject a joint, trying to reestablish a normal environment in the sheath and, ideally, preserve tendon function.

Trotter says many windpuffs respond favorably to ice or some bandage support between competitions and don't need medication. "These efforts are enough to keep them from getting sore," he says. "Otherwise local injections of HA are often beneficial. HA is a normal component of many soft tissues around the joints and tendon sheaths and seems to help reduce swelling and soreness.

"Usually we try to get a needle in the sheath to draw off what fluid we can, then follow up with local injection of HA, followed by a week in support bandages," continues Trotter. "The horse should not be in a stall; he needs controlled exercise while healing, so you can regulate the amount and the speed." Between exercise sessions the horse should be in a confined area so he won't be running or bucking.

"If the annular ligament is the problem, it can be surgically cut ... with the horse standing, or we can do tenoscopy," says Lynch. "We put the arthroscope into the tendon sheath to look at adhesions and treat them by taking them out, or we can transect the annular ligament itself."

Take-Home Message

If your horse has chronic windpuffs, watch them for changes in size and symmetry among the affected legs, and observe whether your horse is uncomfortable. Discomfort and/or heat and swelling could be a sign of acute injury, so call your veterinarian in these scenarios. Effective treatments, from HA injections to annular ligament transection, are available.

About the Author

Heather Smith Thomas ranches with her husband near Salmon, Idaho, raising cattle and a few horses. She has a B.A. in English and history from University of Puget Sound (1966). She has raised and trained horses for 50 years, and has been writing freelance articles and books nearly that long, publishing 20 books and more than 9,000 articles for horse and livestock publications. Some of her books include Understanding Equine Hoof Care, The Horse Conformation Handbook, Care and Management of Horses, Storey's Guide to Raising Horses and Storey's Guide to Training Horses. Besides having her own blog, www.heathersmiththomas.blogspot.com, she writes a biweekly blog at http://insidestorey.blogspot.com that comes out on Tuesdays.

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